Method and device for manufacturing tear-open lids

ABSTRACT

During the manufacturing of tear-open lids out of lid rings with a tear-open foil sealed on it, the tear-open foil having a tear-open tab, the tear-open tab is fixed by means of an adhesive surface which is applied onto the tape before stamping out the tear-open foil out of a band of this material.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the priority of Swiss patent application0061/09, filed Jan. 16, 2009, the disclosure of which is incorporatedherein by reference in its entirety.

FIELD OF THE INVENTION

The invention is related to a method for manufacturing tear-open lids,comprising the steps of: providing a band of tear-open foil material,stamping a foil section with a tear-open tag out of the band, sealingthe foil section onto a lid ring and folding the tear-open tab on thelid. Furthermore, the invention is related to a device for manufacturingtear-open lids as well as to a tear-open lid with a lid ring and atear-open foil.

BACKGROUND-PRIOR ART

It is known to execute lids for can-like or box-like packages as metalcovers which are permanently attached on top of the package, having alid ring with an extraction opening. The latter is kept closed until thefirst use of the package content by means of a foil which is applied onthe lid ring by means of heat sealing and which can be torn open; suchlids are called tear-open lids. The foil on the lid is called tear-openfoil and may for example be a metal foil, a metal composite foil or apure plastic foil. An additional lid made of plastic which is arrangedabove the metal lid makes the package resealable during the use periodof the content. In order to open the tear-open lid or to tear away thesealed foil respectively, the latter has a tear-open tab. When closing acan after its filling, the pre-fabricated tear-open lid is flanged up atthe body of the can. During this manufacturing step, a tear-open tabwhich sticks out may disturb, wrinkle and be even torn off. Furthermore,the appliance of the plastic lid is normally only possible when the tabis fold back. Therefore it is preferred that the tear-open tab is foldback onto the lid and that it keeps this position. This is possible incase of metal foils; however, even in this case, the thermal effect andthe cooling process during the sterilization of the filled and sealedcan may cause a deformation and an undesired sticking out of thetear-open tab. In case of composite foils made of metal and plastic orfoils made only of plastic, a permanent folding back is more difficultand the result is even more likely to be a sticking out during thesterilization, because of different thermal expansions of the layers.For cans receiving dry products which don't have to be sterilized it isalready known to fixate the folded back tear-open foil on the lid bymeans of Hotmelt adhesive material, after having sealed the tear-openfoil on the lid. However, this production step is complex. In addition,it is not usable for cans which have to be sterilized, because Hotmeltadhesive material fails in sterilization conditions.

Known methods or devices respectively for the manufacturing of tear-openlids will be explained in the following by means of the FIGS. 1 to 9.Thereby, the FIGS. 2 to 8 serve for explaining the manufacturing steps.

SUMMARY OF THE INVENTION

The invention has the task of enhancing tear-open lids.

The method mentioned at the beginning solves the task by applying anadhesive surface on the band before stamping out the foil section, at aposition where the folded back tear-open foil comes to lie on thetear-open lid. Furthermore, the task is solved by the manufacturingdevice comprising a conveying installation for lid parts and lids, asealing station wherein a band of tear-open foil material is feedable bymeans of feeding means wherein the sealing station is formed to stampout a foil section with a tear-open tab out of the band and to seal thefoil section with its sealable lower side onto a lid ring, a foldingstation wherein the tear-open tab is foldable onto the lid,characterized in that an installation is provided, by means of which anadhesive surface is applicable on the upper side of the band beforestamping out the foil section. The task is further solved by a tear-openlid with a lid ring and a tear-open foil with a folded back tear-opentab, characterized in that the tear-open tab is attached on thetear-open foil by means of an adhesive surface which is formed from apiece of double sided adhesive tape whose adhesive strength is differenton each of its sides, wherein the lower adhesive strength acts on theside to which the tear-open tab is attached.

It is particularly preferred to apply the adhesive surface in form of apiece of double sided adhesive tape and particularly of an adhesive tapewith a different adhesive strength on each of the adhesive sides,wherein the tape is applied in such a way, that the lower adhesivestrength is effective at the tear-open tab.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, embodiments of the invention will be further explainedby means of the figures.

FIG. 1 is a schematic side view of a device according to the prior artas well as for carrying out the present invention;

FIG. 2 to FIG. 8 are sectors of metal lids for explaining theirmanufacturing;

FIG. 9 is a top view on a tear-open lid according to the invention;

FIG. 10 is a partial section view of the tear-open lid of FIG. 9;

FIG. 11 is a schematic view of the appliance of the tear-open foil inthe sealing station as well as further steps;

FIG. 12 is a schematic view of a stamping station for a double sidedadhesive tape;

FIG. 13 is a schematic section view of the blow and suction equipmentfor removing the protective foil from the adhesive surface; and

FIG. 14 is a more detailed view of the removal of the protective foil.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a schematic side view of a device 1 for manufacturingtear-open lids. It has multiple processing stations 3 to 9 on a machineframework 2. A conveying installation 10, 13, 14 transports lid partsand the finished lids in a conveying direction indicated by the arrow C,from the input of the device at the stack 11 to the output of the devicewhere the lids reach the trays 16 or 17 via slides. Lid parts aredestacked from the stack 11 in a known way and they get into theconveying installation. The latter may have two long bars 10, each ofwhich is arranged at the side of the objects and lift up the lid partsor the lids respectively lying on the trays 10′ or in the stations to 9respectively, during their own lift up, in the direction of arrow A, bymeans of the actuator 14, and subsequently shift them onwards by anamount in a forward motion in the direction of arrow B (in the samedirection as arrow C) by means of a crank drive 13. Thereafter, the barsare moved downwards in the direction of arrow A, wherein the lid partsor the lids respectively are again placed onto their laydown position.Thereafter, the bars 10 are moved backwards below the object laydownpositions in the direction of arrow B and antiparallel to arrow C,whereafter the described process is repeated. Between transportations,the lid parts or the lids respectively lie on their laydown positions orare located in the processing stations respectively and are processedthere. A recurring conveying takes place after a processing step throughall processing stations. A known conveying installation with two toothbelts according to WO 2006/017953 may be used instead of the describedconveying installation. Such an endless tooth belt drive has thenecessary length for the number of processing stations and the stepwisetooth belt motion which is synchronized with the processing stations isdone by means of a step motor or a servo motor, which actuates the toothbelts by means of pulleys. The conveying installation with tooth beltsmakes it possible to manufacture lids with a higher cycle number of forexample 200 lids per minute.

FIG. 2 shows stacked metal lid blanks 20, as they are provided in thestack 11 at the beginning of the conveying installation. These blanks 20are for example round metal disks with a diameter of for example 11 cm.Evidently, other basic shapes like for example square or rectangulardisks and other diameters are readily possible. The blanks 20 havealready been preformed at their edge in a processing machine which isnot shown, as shown in FIG. 2. In FIG. 2 and in the subsequent FIGS. 3to 9, only a sector of the whole disk or lid respectively is shown inorder to simplify the figures. In the first processing station 3 of FIG.1, an opening is stamped into the disk by means of a stamping processwith an upper and a lower tool, this being shown in FIG. 3, wherein theedge of the opening is denoted by 21 and the stamped out round disk by27. This disk 27 is disposed of in the container 12 of FIG. 1. Thus, theresult is a ring shaped lid part 20′ with an opening which forms theextraction opening of the finished lid. The stamp processing station 3is actuated—as it is the case for the additional processing stations—bymeans of an actuator 15. A pulling down of the edge 21 takes place inthe processing station 4, by means of which for example the shape 22 ofthe edge, shown in FIG. 4, is reached. The ring shaped lid parts 20′then reach the sealing station 5. Therein, a foil section 25 is stampedout by means of stamping means 6, placed above the opening of the lidring 20′ and attached there by means of heat sealing, this being shownin FIGS. 5 and 6. For this, a sealable plastic layer is applied onto thelower side of the tear-open foil 25 in a known way, wherein the lattermay be a metal foil, a composite foil or a plastic foil. The tear-openfoil 25 may for example be a multiple layer composite foil with plasticlayers and aluminium layers and may for example have a layer of heatsealable polypropylene (PP) and a subsequent layer of PET, beingfollowed by an aluminium layer and having another PET layer on the upperside of the tear-open foil. A possible print is arranged under this PETlayer. A further embodiment of the tear-open foil may be a heat sealingpaint layer arranged under the lid or on the contents side respectively,being followed by the aluminium layer and the PET layer on the upperside of the lid. Also further embodiments are known to the skilledperson and may be used within the scope of the present invention. Theneeded precut foil 25, which in this example has a round shape, isnormally stamped out of a wide foil web in the station 5, 6, placedabove the middle cavity of the ring shaped disk, wherein the foil ispressed by the sealing station at the edge of the round cavity of thelid part 20′ under the influence of heat, such that the foil 25 issealed tightly by melting and subsequent cooling of the sealable layer.This is known and will therefore not be explained in more detail. Thetear-open lid 28 is thereby formed. A cooling process station 7 maypossibly be provided for the cooling. The foil 25 may be provided with astamp 24 (FIG. 7) in the processing station 8 and then the edge 22 issubsequently flanged to yield the finished edge 23. If the tear-openfoil is provided with a tear-open tab, the tab may then be folded backsuch that it comes to lie on the lid. The finished lids are submitted toan inspection in an inspection station 9 which is to be considered aprocessing station, normally comprising a leak test for the tear-openfoil 25 which is applied on the lid, wherein an air pressure gradient iscreated between the lower side and the upper side of the lid. If thefoil is tightly attached to the lid ring, the lid thereby ends up in thetray 16 for the finished lids. If a leak is detected, the lid ends up inthe waste container 17 via the other shown slide.

FIG. 9 shows a finished tear-open lid 28 in a top view. Thereby, thetear-open foil 25 has a tear-open tab 29 which is folded back onto thelid. According to the invention, the tear-open tab at the lid isattached by means of an adhesive surface 30 which is preferably formedby a double sided adhesive tape, particularly with different adhesivestrengths of each of its tape sides. An adhesive surface formed by asealing paint may also be provided. FIG. 10 shows a zoomed view of thearea of the tear-open lid with the tear-open tab 29 which, in its foldedback position, is detachable attached to the adhesive surface formed bya piece of double sided adhesive tape. The tab 29 sticks out over theadhesive surface 30, such that the tab for opening the tear-open lid maybe grasped and detached from the adhesive surface 30 in a simple way.The adhesive tape 33 is preferably differently adhesive on each of itssides, such that the bond of the adhesive tape on its lower side (shownin FIG. 10) or at the tear-open foil surface respectively, is higherthan at its upper side to which the tear-open tab 29 is held in anadhering way. This makes sure that the tab 29 may easily be removed fromthe adhesive surface, while the adhesive tape remains bonded on thetear-open foil of the lid. In this example, the edge of the extractionopening has a different shape 23′ than in FIG. 7.

The procedure of providing a preferred adhesive surface 30 in form of apiece of double sided adhesive tape on the tear-open lid is explained inFIG. 11. Different types of adhesive surfaces, like particularly sealingpaint surfaces, may be applied as well. FIG. 11 shows in a broadschematic way a part of a device for manufacturing tear-open lids, whichmay for example be a device according to FIG. 1. Four rows of lid parts20, 20′ or lids 28 respectively are conveyed parallel in the conveyingdirection C by means of the conveying installation which is not shown inFIG. 11. In the area of the sealing station which is not shown here asan apparatus (accordingly like the sealing station 5 and 6 of FIG. 1) aband 35 of the tear-open foil material runs into the sealing station andis stamped there, in order to form the foil sections 25 with thetear-open tab 29. The stamping pattern is thereby chosen in such a waythat as little stamping waste as possible is left over. The foilsections 25 for the uppermost row of lid rings 20′ of FIG. 11 are inthis example stamped out of the band 35 in the leftmost row at the edgeof the band. After that, the empty regions 25′ are left. The foilsections 25 for the second uppermost row of lid rings 20′ are stampedout in the row left of the middle axis of the band 35 and the foilsections for the second lowest row of lid rings 20′ are stamped out inthe row right of the middle axis of the band 35. The foil sections 25for the lowest row of lid rings 20′ are stamped out in the rightmost rowof the band 35. The stamped out foil sections are each sealed onto therespective lid ring, as known to the skilled person. The band 35 may beconveyed by means of actuating rollers 36 or by other known means. Theadhesive surfaces 30 are applied onto the band 35 on its upper side 26before the stamp out of the foil sections 25. This takes place in such away, that at least one such adhesive surface is applied onto the band 35at each foil section 25 which has to be stamped out later, namely at theposition on the foil section 25, whereat the folded back tab 29 of thefinished tear-open lid 28 comes to lie. The stamping of the individualfoil sections 25 in the sealing station may for example be controlled bymarks printed on the band. These printed marks may also be used ashelpers for the correct positioning of the adhesive surfaces 30, ifnecessary. However, a print on the tear-open foil sections themselvesmay serve as a mark.

In the shown example, a double sided adhesive tape is guidedtransversally to the tear-open foil band 35 over the same. This is apreferred example, the adhesive tape could however be also guidedobliquely or in the same direction over the band 35. Also multiplesingle bands could be provided instead of a tape 33. The double sidedadhesive tape has no protective foil at its lower side located oppositeof the band 35, which preferably has the higher adhesive strength thanthe upper side. On the contrary, a protecting foil 37 is provided on theupper side, being shown in the top view of FIG. 11. A double sidedadhesive tape with a respective different adhesive strength on bothsides and with a single sided protective foil on the side with a loweradhesive strength, being adequate for being applied on the band 35, isfor example the adhesive tape tesafix 6917 of the company teas bandfixAG, Bergdietikon, Switzerland. This adhesive tape is knowingly used forthe reversible sealing of foil bags. The adhesive tape running over theband 35 is stamped by means of a stamping installation (FIG. 12), suchthat the adhesive surfaces 30 are stamped out of the adhesive tape 33.Preferably, they are applied directly onto the band 35 by the stampingtool, where they stick by means of their lower side which is free ofprotective foil. The upper side of each adhesive surface stays coveredby means of the equally stamped protective foil 37. The empty regions33′ remain in the tape 33.

As shown in FIG. 11 in case of the tear-open lids which are viewable inconveying direction C directly after the band 35, an individual lid 28is formed in this way, with a tear-open foil 25, from which a tab 29sticks out over the edge of the lid and whereat an adhesive surface 30,which is still covered by a protective foil 37, is provided. Thereby theprotective foil 37 allows a failure-free sealing of the tear-open foil25 onto the lid ring and protects the adhesive surface 30.

After that, the protective foil 37 is removed and the tab 29 is foldedback onto the free adhesive surface 30, where it is fixed by theadhesive material, leading to the lid 28 shown in FIGS. 9 and 10. In theexample of FIG. 11, the removal of the protective foil 37 takes place inthe station 40 and the folding back of the tab 29 in station 41. Inbetween, the lid is turned into a defined position for the folding back,which may however be equally done before. The lid 28 with the adheringand folded back tab is viewable at the end of the conveyor line of FIG.11. The folding back of the tab is already known to the skilled personand is not explained in more detail here. On the other hand, thestamping out of the adhesive regions and the removal of the protectivefoil 37 is elaborated in more detail in the following.

Equally, an adhesive surface in form of a surface 30 of sealing paintmay be provided for fixing the tab 29 onto the lid 28 instead of thepreferred double sided adhesive tape. An adhesive material may also beapplied instead of a sealing paint. The adhesive surface 30 is alsoapplied onto the band 35 before the stamping out of the foil section 25and the applying on a region of the band 35, onto which the tab 29 isbeing folded back for the finished lid 28, also takes place in thesecases. The sealing paint or the adhesive material may be imprinted onthe band 35, for example by means of printing rollers or by means of padprinting or they may be sprayed on it. This may occur directly beforethe sealing of the foil section 25, as shown in FIG. 11 for the adhesivetape. The applying of the adhesive surface 30 by means of sealing paintor of an adhesive material may however take place beforehand,particularly during the manufacturing of the band 35 out of thetear-open foil material, wherein a covering with a protective foil maybe provided in case of using an adhesive material, this not beingnecessary in case of forming the adhesive surface 30 with sealing paint,because the latter doesn't cause an adherence until the sealing.

A further sealing process at the adhesive surface 30 is necessary incase of the sealing paint, when the tab is folded back. This may takeplace in the station wherein the stamping is applied (FIG. 7). Aseparate sealing station for this step may also be provided, for exampleinstead of the removal of the protective foil shown in FIG. 11, whereinin this case 40 may identify a station for folding back and sealing ofthe tab 29 and the station 41 would be obsolete.

FIG. 12 shows the stamping out of the parts of the double sided adhesivetape 33 forming the adhesive surfaces 30. The double sided adhesive tape33 is peeled off from a roll 34 and lead over the band 35, this beingviewable in FIG. 12 as a cut from the drawing plane. The band 35 runsover a supporting surface 36 in the region of the four actuated stampingmachines 38, in order for the stamping tools to be able to press thestamped out piece of adhesive tape onto the band 35. The structure ofactuated stamping tools 38 for the adhesive tape 33 is a technicalmeasure. The tape 33 is not adhering on the surface of the tape 33because of the protective foil 37, such that the stamp of each stampingtool doesn't have to be protected against an adherence to the adhesivetape. The lower side of the adhesive tape is adhesive, such that the dieand the vicinal regions of the stamping tool have to be furnished withan anti-adherence coating, for example a Teflon coating, in order forthe adhesive tape not to adhere to the die or to its vicinity during thestamping out.

The removal of the protective foil 37 from the adhesive surface 30 isexplained by means of FIGS. 13 and 14. For this, on the one hand, an airjet 43 is blown obliquely from the side onto the adhesive surface 30,thus lifting and loosening the protective foil. On the other hand, asuction flow 46 is generated and therefore air above the adhesivesurface is aspirated, thus removing the loosened protective foil 37.FIGS. 13 and 14 show a partially cut view of a station 41 without theconveying installation or the support means for the lid 28 respectively.Preferably, the pressurized air, indicated with arrows 43, is blownaround and obliquely onto the border of the adhesive surface 30 via anannular nozzle 44. The border of the adhesive surface is preferablyenlarged compared to a round adhesive surface, by stamping out theadhesive tape star-shaped or toothed wheel shaped. This enhances theremoval of the protective foil 37 from the adhesive tape if the air isblown from the side on the adhesive surface. A suction opening 45arranged centred above the adhesive surface 30 can suck off the loosenedprotective foil 37 by means of a suction flow 46 generated by underpressure. Additionally to the removal of the protective foil 37 by meansof air, a mechanical removal by means of grippers or fingers may beprovided, lifting the protective foil at least at the border of theadhesive surface.

During the manufacturing of tear-open lids 28 out of lid rings 20′ withsealed tear-open foil 25 with a tear-open tab 25 on it, the tear-opentab is thereby fixed by an adhesive surface 30 which is applied out of aband 35 of this material onto the tape. In this way, a simple andsuitable tab fixing for the production of tear-open lids with high speedresults.

1. A method for manufacturing tear-open lids, comprising the steps of:feeding in a band of tear-open foil material; stamping a foil sectionwith a tear-open tab out of the band; sealing the foil section onto alid ring; and folding back the tear-open tab onto the lid, characterizedby the step of: applying an adhesive surface on the band before stampingout the foil section, at a position where the folded back tear-open tabcomes to lie on the tear-open lid.
 2. The method according to claim 1,wherein the adhesive surface is applied as a piece of a double sidedadhesive tape.
 3. The method according to claim 2, wherein an adhesivetape is applied, which has different adhesive strengths on each of itssides, wherein the adhesive strength on the side facing the tear-opentab is smaller.
 4. The method according to claim 2, wherein the pieceabove the band is stamped out of the adhesive tape and applied on theband directly after that.
 5. The method according to claim 2, whereinthe adhesive tape has a protective foil on its upper side, which isremoved before folding back the tear-open tab.
 6. The method accordingto claim 5, wherein the protective foil is loosened by means of at leastan air jet and the loosened protective foil is sucked off by means of asuction flow.
 7. The method according to claim 1, wherein the adhesivesurface is applied in liquid form.
 8. The method according to claim 7,wherein a sealing paint is applied as adhesive surface and wherein asealing for the fixing of the tab takes place while folding the tab backonto the lid.
 9. The method according to claim 8, wherein the sealingpaint is applied as adhesive surface by printing.
 10. The methodaccording to claim 8, wherein the sealing paint is applied as adhesivesurface by spraying.
 11. A device for manufacturing tear-open lids,comprising a conveying installation for lid parts and lids, a sealingstation wherein a band of tear-open foil material is feedable by meansof feeding means wherein the sealing station is formed to stamp out afoil section with a tear-open tab out of the band and to seal the foilsection with its sealable lower side onto a lid ring, a folding stationwherein the tear-open tab is foldable onto the lid, characterized inthat an installation is provided, by means of which an adhesive surfaceis applicable on the upper side of the band before stamping out the foilsection.
 12. The device according to claim 11, wherein the installationhas at least a feeder for at least an adhesive tape as well as at leasta stamping tool by which the adhesive surface is stampable out of theadhesive tape and applicable on the upper side of the band.
 13. Thedevice according to claim 11, wherein an equipment for removing aprotective foil from the adhesive surface is provided.
 14. The deviceaccording to claim 13, wherein the equipment is formed to applypressurized air to the adhesive surface and to suck off the loosenedprotective foil.
 15. A tear-open lid with a lid ring and a tear-openfoil with a folded back tear-open tab, characterized in that thetear-open tab is attached on the tear-open foil by means of an adhesivesurface which is formed from a piece of double sided adhesive tape whoseadhesive strength is different on each of its sides, wherein the loweradhesive strength acts on the side to which the tear-open tab isattached.